Lifetime prediction model of thermal fatigue stress on crystalline silicon photovoltaic module

Thermal cycling stress can result in fatigue cracks of interconnections between ribbon wires and the metallization of a photovoltaic (PV) module, thereby increasing its series resistance. Therefore, in this study, the thermal cycling (TC) history of PV modules exposed to two benchmark climate (Phoenix, AZ) has been derived employing corresponding meteorological data. Using the three parameters rain-flow counting algorithm, the number of TCs versus temperature change was calculated over one year. The number of rain-flow cycles was 935 in Phoenix. Furthermore, three types of accelerated tests were conducted to develop a lifetime prediction model. The Basquin equation was used to predict the number of cycles to failure, based on stress calculation. A finite element model for stress analysis was developed. Failure analysis shows that crack occurred at the solder joint after accelerated test.